Jet sound suppressing means



c. E. LANGsToN, JR 3,463,402

JET SOUND sUPPREssING MEANS 4 Sheets-Sheet l Aug. 26, 1969 Filed Dec.28, 1966 Aug 26,` 1969 c. E. LANGsToN, JR 3,463,402

JET SOUND SUPPRESSING MEANS Filed Deo. 28, 1966 4 Sheets-Sheet 2 U8 261969 c. E. LANGsroN, JR 3,463,402

JET SOUND SUPPRBSSING MEANS Filed Dec. 28, 1966 4 Sheets-Sheet 3 Aug.26, 1969 c. e. LANGs'roN. JR

.JETSOUND sUPPRr-:ssmo MEANS Filed Dec. 28, 1966 4 Sheets-Sheet UnitedStates Patent O i 3,463,402 JET SOUND SUPPRESSING MEANS Chandos E.Langston, Jr., North Palm Beach, Fla., as-

signor to United Aircraft Corporation, East Hartford,

Conn., a corporation of Delaware Filed Dec. 28, 1966, Ser. No. 605,454Int. Cl. B64d 33/06; B64c 15/10 U.S. Cl. Z39-265.13 13 Claims ABSTRACTOF THE DISCLOSURE A gas turbine engine having an exhaust iiow meanswhich will reduce the perceived noise level associated with thedischarge of a high velocity gas jet or jets. An exhaust duct havingflaps at the rear end thereof having a pod thereon onto which blow-indoors are pivotally mounted to open inwardly toward said duct. Anannular body being positioned rearwardly of said pod with its innersurface forming an inlet passageway with each blow-in door when it is inits inward position. Nozzles means are located in the annular body for abalance between engine performance and noise suppression. Means areprovided for inducing turbulence where the blow-in doors end in aninward position. Said turbulence inducing means can comprise means fordirecting a gas flow into said passageways or involve some other deviceswhich project into said passageways.

This invention relates to means for reducing the perceived noise levelassociated with the discharge, usually through an ejector shroud, of ahigh velocity gas jet or jets primarily from a gas turbine engine.

It is an object of this invention to provide a blunt base region at theplace where two streams of gas, which are flowing at high but dissimilarvelocities, are permitted contact therebetween.

It is another object of this invention to provide means for generating athick region of vorticity around an expanding gas jet.

It is a further object of this invention to provide a gas outlet on agas turbine engine with a configuration having a large blunt areaseparating the terminal part of the inner surface of an annular gaspassage surrounding a nozzle and the rear edge of the convergent nozzle.

It is another object of this invention to provide a duct having aprimary gas fiow with a converging nozzle with turbulence inducing meanslocated in an annular passageway surrounding said rear end of said ductand said nozzle admitting tertiary air.

It is a further object of this invention to provide means for injectinggas into the tertiary flow admitted through blow-in doors at a pointwhere turbulence is desired.

It is another object of this invention to provide blow-in doors or afixed ramp of an annular passage around a converging nozzle with aroughened surface in order to initiate turbulence or flow separation.

It is a further object of this invention to provide a surface around theconverging nozzle which can be used for the ow, separating from a pointforward of said surface to attach to, so that it can separate a secondtime. It is another object of this invention to provide an engine havinga central primary flow and an annular primary flow therearonnd with ablunt surface between the two primary flows where they are permitted tocome together with blow-in doors arranged to provide an effective bluntsurface between the annular primary flow and the tertiary air beingadmitted.

It is a further object of this invention to provide clamshells within afixed annular body mounted rearwardly Patented Aug. 26, 1969 ICC of apod enclosing an engine having a primary central flow and a primaryannular flow therearound, said clamshells being adjustable to achieve anoptimum balance between noise attenuation and nozzle performance.

It is another object of this invention to provide an ejector nozzlethrough which one or more central primary ows and a tertiary fiow pass.The exit area of said ejector being Set in or adjusted to an optimumposition to obtain the most favorable balance between noise attenuationand nozzle performance.

It is a further object of this invention to provide actuating means forvarying the position of clamshells mounted within a fixed annular body,or shroud, so that they can be placed at some predetermined positionwhen desired.

It is another object of this invention to provide actuating means forvarying the position of flaps mounted around the exit of a fixed annularbody or shroud to place the Cflaps in a predetermined operating positionwhen desire Other objects and advantages will be apparent from thespecification and claims and from the accompanying drawings whichillustrate an embodiment of the invention.

FIGURE l is a longitudinal schematic view of the exhaust section of ajet engine showing the invention.

FIGURE 2 is a view showing a modification of FIG URE l which provides anannular liange to permit airow around a nozzle at the end of a ramp.

FIGURE 3 is an enlarged view showing a mechanism for varying thedirection of an air jet around a nozzle.

FIGURE 4 is a view taken along the line 4-4 of FIG- URE 3 while alsoshowing the slots.

FIGURE 5 is a view showing a modification of FIG- URE 2 which providesan annular flange to permit airflow around the nozzle and provides anannular trip extending into the outer airfioW.

FIGURE 6 is a view showing a modification of FIG- URE l with the rampleading into the nozzle having a roughened surface.

FIGURE 7 is a view showing a modification of FIG- URE l wherein a secondattaching surface is fixed to the converging nozzle portion.

FIGURE 8 is a view showing the invention applied to an engine having twoprimary gas liows, one through an inner duct and one through an annularduct around said inner duct.

As stated hereinbefore, FIGURE l shows the rear end of a conventionalhigh speed aircraft jet engine 12. Engine 12 is of a conventional designand may be of the type described more fully in vU.S. Patent No.2,747,367. The primary duct 26 has at its downstream end an eX- haustnozzle 48 forming an outlet. While the exhaust nozzle 48 is shownconsisting of a number of sectioned pieces 10 positioned at a fixedangle, this exhaust nozzle 48 may be made up of movable aps so sectionedand adapted to move to other positions (note U.S. Patent Nos. 3,062,003;2,815,643 and 2,836,034). The exhaust nozzle 48 is shown fixed in thisposition since it is in this position during takeoff, and other timesdemanding high power, and it is at this time that noise attenuation ismost desirable.

An annular manifold 32 extends around the rear end of the primary duct26 adjacent the location where the aps 10 of the nozzle 48 are connectedto the primary duct; said manifold 32 includes a plurality of openings3=8 through which a fluid can be injected to make sure that owseparation occurs at that point. The manifold is consrtucted having araised center so that a step is formed where the blow-in doors 44 end,and the flaps 10 for nozzle 48 begin, to start the flow separation.

The engine 12 has a nacelle or pod 34 around it with a fixed member 40positioned axially downstream of the nacelle or pod 34. This xed member40 can be supported from means associated with the engine such as by aplurality of axially extending struts, or the fixed member 40 can beattached to parts of the aircraft structure. A plurality of sealably,overlapping, and circumfcrentially positioned pivotal blow-in doors 44are positioned between the end of pod 34 and the forward part of fixedmember 40. In their outermost position, the blow-in doors extend betweenthe end of the pod 34 and the forward part of fixed member 40 to providea continuation of the pod 34 to the outer surface 84 of the fixed member4). The blow-in doors 44 move inwardly until their rear ends touch ornearly touch the rear portion of the engine at the top of the raisedmanifold 32 adjacent the attachment -point of the flaps 48 formingastep. While the blow-in doors 44 and the flaps 46 extending from therearward end of the fixed member 40 are shown as free floating, they maybe power actuated.

The nozzle 48 is the primary nozzle and the nozzle .formed by the fixedmember 40 and aps 46 is the secondary nozzle. As seen in FIGURE l, theprimary nozzle 48 has its flaps 10 positioned inwardly and the blow-indoors are located inwardly with the rear ends thereof positioned againstthe manifold 32 thereby forming an annular inwardly extending ramp whilethe flaps 46 are angled inwardly.

For takeoff, an engine having the elements as shown in FIGURE 1 shouldhave them in the position as shown. That is, the flaps 10 forming theprimary nozzle 48 are located essentially as shown, i.e., to form ablunt base region surrounding the nozzle throat (radius r1), and blow-indoors 44 are located in an inward position forming the annular ramp asshown with the inner ends of the doors resting or held on or above theraised portion of the manifold to create a step where the flaps 10extend inwardly from the end of the duct 26. With the flow of tertiaryair through the annular passageway formed between the blow-in doors 44and the forward inner surface f the fixed member 40, a turbulent sheerlayer is started at the step formed at the end of the duct 26 whichgrows into the turbulent sheer layer extending from the annular end ofthe nozzle 48. The rapid growth of the turbulent sheer layer providessound suppression by reducing the area of the surface over which thesound is being emitted. To aid in the growth of the turbulent sheerlayer extending from the rear end of the nozzle 48, a gas can beinjected through the openings 38. The gas is brought from an inlet pipe14 through a control 16 and outlet pipe 18 which is connected to themanifold 32. The control 16 can be automatically controlled by an engineparameter such as a power setting, or it can be manually operated ifdesired. Inlet pipe 14 can be connected to an engine compressor stage orsome other source of high pressure gas.

FIGURE 2 is a modification of FIGURE 1 wherein the manifold 32 isreplaced by a solid annular flange 50 having spaced projections 52extending therefrom. It can be seen that when the end of blow-in doors44 engage the tops of the spaced projections S2, space is provided forthe injection of a gas which could be directed between the inside ofblow-in doors 44 and around the primary duct 26. It can be seen that amore pronounced step is formed by this arrangement.

As a modification to FIGURE l wherein the gas jets are located at afixed angle with respect to the primary duct 26, FIGURES 3 and 4 showmeans for varying the angle at which a gas jet is injected.

In this modification, the exit end of the primary duct 26 is shaped as apolygon with each side having a mounting sleeve 60 with a movablemanifold section 62 therein. Adjacent ends of mounting sleeves 60 areconnected by Wedge-shaped nieces of conduit 6l which are xed in placeand sealed so that iiuid ow can pass between manifold sections `62. Aplurality of the pieces of conduit 61 have an opening 63 therein whichwould be connected to a source of gas such as pipe 18. Each mountingsleeve 60 has a large slot 64 extending from a line parallel to thesurface of the blow-in door 44 upwardly for a range of about 50 aboutthe centerline of said sleeve. Each movable manifold section has a longnarrow slot 66 or a line of holes for directing gas flow from theinterior of the section through slot 64. An arm 70 extends from thecenter of each manifold section 62 forwardly through an opening 72 ineach sleeve member 60.

An elongated slot 74 is located along the free end of each arm 70. Abell crank 76 mounted for pivotal movement to the top of a bracket 78fixed to duct 26 has one arm 80 with a pin 82 which rides in the slot74. The other arm 86 of the bell crank lever is pivotally connected to atab on a synchronizing ring 88. The ring 88 is moved backwards andforward in accordance with movements of a plurality of links 90.

It can be seen that as the links 90 of this system are moved rearwardly,the lower ends of all of the arms 86 go rearwardly Vand the arms 80 moveupwardly with the pins 82 moving the arms 70 upwardly to lower the flowfrom 66. As the links 90 of this system `are moved forwardly, the lowerends of all of the arms 86 go forwardly and the arms 80 move downwardlywith the pins 82 moving the arms 70 downwardly to raise the flow from66.

FIGURE 5 is a modification of FIGURE 2 where the rearward part of thetops of projections 52 have an annular projection 53 extending outwardlytherea-round to form a trip at that location to further aid in startingflow separation and increasing turbulence. An annular fla-nge 101extends around the outer end of duct 26 having a sealing material 103around the outer edge. As the blowin doors come inwardly, they cont-actthe sealing material 103 along their length and the ends rest againstthe projections 52. Gas can be injected into the chamber formed by theduct 26, blow-in doors 44, fiange 50, and flange 101 through openings inthe flange 101. As in FIGURE 1, the pipes 18 can be connected thereto.

FIGURE 6 differs from FIGURE 1 in that the downstream portion of theouter surface of each blow-in door is roughened as at 45. The rougheningneed not be too severe. This roughening provides an additional means forcreating turbulence.

FIGURE 7 adds a second attaching surface to each flap 10 of the nozzle48 so that when the fiaps are in their innermost position, a surface isformed around the nozzle so that the flow which separates at the rearend the ramp formed by blow-in doors 44 will attached thereto and thenseparate again. This action increases the level of turbulence as desiredto promote rapid growth of the sheer layer surrounding the expandingjet.

FIGURE 8 shows the incorporation of applicants device on an engine suchas shown in U.S. Patent No. 3,338,051. This engine is of a type whereinan annular duct extending rearwardly from the fan of a fan engineincludes a duct burner wherein heat is added to the bypass air forincreasing augmentation of the stream. An engine of this type has twoprimary gas iows, one from the conventional jet engine and one from thesurrounding annular duct burner. The engine shown has an annular duct 6formed by an outer wall 8 and an inner wall 12. The inner wall 12extends around a jet engine or gas generator having an outer wall 20with a center cone 22 positioned therein by struts 24. The end of theouter wall 20 forms a converging-diverging section and the rear part ofthe inner wall 12 of duct 6 ends in a plug surface along which the gasfiowing through duct 6 expands as in a conventional plug nozzle. Therear end of each of these walls, 12 and 20, are connected by an annu;lar blunt base 28,

A track mechanism 30 is located in a fixed position around the end ofthe outer wall 8 which has a plurality of flaps 33 slidably mountedthereon to provide a nozzle capable of having its converging anglevaried. An actuator (not shown) provides movement of rods 31. A pod ornacelle 35 encircles the engine and has a plurality of blow-in doors 37.The blow-in doors 37 are constructed of two parts, a forward section 37aand a rearward section 37b. The front part of each forward section 37ais pivoted at the rear of the pod or nacelle 3S.

An annular fixed member, or shroud, 39 is spaced downstream from the pod35 so that the forward edge thereof is adjacent the trailing edges ofthe blow-in doors when they are in their outermost position completingthe outer pod surface (dotted position in FIG. 8). Flaps 41 arepivotally attached to the rearward end of the annular member 39 tochange the exit opening. Asshown, the rear part of a section 37a and theforward part of a section 37b are pivotally connected at 54. The hingepoint of each blow-in door has a roller 56 at each side which travels ina cam opening which is part of the connecting linkage between all of theblow-in doors and the two clamshells 43 of a clamshell nozzle which ismounted Within the annular member, or shroud, 39. A linkage (not shown)between the two clamshells 43 and the blow-in doors could be used whichpermits the :movement of the blow-in doors between the solid positionshown in FIGURE 8 and the dotted position to move the clamshells betweentheir solid position and their dotted position. The solid position ofthe blow-in doors 37, clamshells 43, and flaps 41 represents theirlocation when the engine is in subsonic Hight and the position of themembers is dotted outline shows their respective locations duringsupersonic flight.

A turbulence inducing means is provided in each of walls 12 and 20upstream of the blunt base 28 to increase the rate of growth of theturbulent sheer layer which lies between the gas generator dischargestream Iand the fan stream over and above that which would result fromthe blunt base 28 alone. The turbulence inducing means shown consists ofslots or holes 45 and 47 to which a gas can be directed by a pluralityof pipes 49 and 51, respectively. Pipes 49 and 51 are connected to anannular manifold 58 which is fed from a source of gas under pressure byconduit 55.

A turbulence inducing means is provided to induce a turbulent regionleaving the blowin doors 37. The turbulence inducing means shown is anannular manifold 57 xed to the rear of the track mechanism 30 withopenings 59. This manifold 57 is fed a gas under pressure in the samemanner as manifold 53.

Further attenuation of jet noise is provided by adjustment of thepositions of clamshells 43 and iiaps 41 relative to the blow-in doorsand to each other. The linkage between the clamshells and blow-in doorscan be adjusted so that the position of the blow-in doors as shown insolid line can position the clamshells to a specific position within arange of positions. The position of these parts being adjusted toprovide the optimum balance between performance (thrust) and noise.

If there were no linkage between the clamshells and blow-in doors, theclamshells 43 could be power actuated so that they could be placed in apredetermined position to achieve the optimum balance referred to above.Further, the aps 41 could be power actuated so that they could be placedin a predetermined position to achieve the optimum balance referred toabove. The precise positioning of the blow-in doors, clamshells andflaps 41 can only be given for a specific engine. The positioning ofthese elements will vary from engine to engine. It would be necessary toactually have tests made of a particular engine to determine precisepositioning of the blow-in doors, clamshells and flaps to achievedesired positions for maintaining a proper balance between performanceand noise.

A specific linkage between clamshells and blow-in doors is shown incopending application Ser. No. 605,453, filed herewith, to Richard E.Teagle, for Engine Exhaust Controller.

I claim.

1. In combination:

(a) an engine having a duct for a first exhaust gas (b) an annular ductsurrounding said first-named duct for a second exhaust gas flow.

(c) flaps positioned to form a convergent section adjacent the end ofsaid annular duct,

(d) a casing surrounding said annular duct having blow-in doorspivotally mounted to move inwardly to a point adjacent said flaps,

(e) the ends of said blow-in doors being located rearwardly outward ofthe ends of said flaps when said blow-in doors are at an inwardposition,

(f) said rst duct having a blunt end separating the ow from the firstduct and annular duct,

(g) an annular body position rearwardly of said blowin doors with theouter surface thereof arranged to be an extension of the blow-in doorswhen they are in their closed position,

(h) nozzle means mounted within said annular member and being movable toa position forming a coverging nozzle when the blow-in doors are intheir inward position,

(i) trailing edge flaps being connected to the downstream end of theannular member, and

(j) means for inducing turbulence where the blow-in doors end in aninward position.

2. In combination, an engine as set forth in claim 1 wherein:

(k) said turbulence inducing means includes means for directing a ow offluid rearwardly adjacent the ends of the blow-in doors to mix with uidow passing throuhg the openings made by said blow-in doors.

3. In combination, an engine as set forth in claim 1 wherein:

(k) said turbulence inducing means comprises an annular manifold fixedlypositioned adjacent the end of said annular duct having openingsdirected rearwardly along the underside of the blow-in doors.

4. In combination, an engine as set forth in claim 1 wherein:

(k) means are provided for directing a flow of fluid rearwardly over theouter edge of the blunt end of the lirst duct.

5. In combination, an engine as set forth in claim 1 wherein:

(k) means are provided for directing a ow of uid along the inner edge ofthe blunt end of the first duct.

6. In combination, an engine having:

(a) a duct for exhaust gas flow,

(b) aps positioned to form a converging section adjacent the end of saidduct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extendingrearwardly, said doors being movable inwardly to a point adjacent saidflaps,

(e) an annular body positioned rearwardly of said pod with the innersurface of said body forming an inlet passageway with each door,

(f) means for inducing turbulance where the doors end in an inwardposition, and

(g) said annular body having nozzle sections mounted therein which aremovable to vary their position in forward tiight to provide an optimumbalance between engine performance and noise suppression.

7. In combination, an engine having:

(a) a duct for exhaust gas flow,

(b) flaps positioned to form a converging section adjacent the end ofsaid duct,

(c) a pod around said duc-t,

(d) blow-in doors pivotally mounted at the end of said pod and extendingrearwardly, said doors being movable inwardly to a point adjacent saidflaps,

(e) an annular body positioned rearwardly of said pod with the innersurface of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in an inwardposition, and

(g) said turbulence inducing means including a preroughenend surface onthe downstream surface of the blow-in doors facing the annular body.

8. In combination, an engine having:

(a) a duct for exhaust gas ow,

(b) flaps positioned to form a converging section adjacent the end ofsaid duct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extendingrearwardly, said doors being inwardly to a point adjacent said llaps,

(e) an annular body positioned rearwardly of said pod with the innersurface of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in an inwardposition, and

(g) said turbulence inducing means including a radially extending flangeadjacent the end of the blow-in doors which extend outwardly into theinlet passageways.

9. In combination, an engine having:

(a) a duct for exhaust gas flow,

(b) flaps positioned to form a converging section adjacent 4the end ofsaid duct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extendingrearwardly, said doors being movable inwardly to a point adjacent saidflaps,

(e) an annular body positioned rearwardly of said pod with the innersurface of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in an inwardposition, and

(g) said turbulence inducing means including a builtup surface locatedmidway on the outside of each flap downstream from the ends of saidblow-in doors to provide a second attaching surface area for holding theflow from the lower portion of the ow passing through the inletpassageways.

10. In combination, an engine having:

(a) a duct for exhaust gas ow,

(b) aps positioned to form a converging section adjacent the end of saidduct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extendingrearwardly, said doors being movable inwardly to a point adjacent saidaps.

(e) an annular body positioned rearwardly of said pod with the innersurface of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in an inwardposition, and

(g) a second duct being located within said duct for exhaust gas flow,

(h) said second duct having an elfective blunt end to separate flowpassing through said duct for exhaust gas liow and said second duct.

11. In combination, an engine having:

(a) a duct for exhaust gas iiow,

(b) aps positioned to form a converging section adjacent the end of saidduct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extendingrearwardly, positioned inwardly to a point adjacent said flaps,

(e) an annular body positioned rearwardly of said pod with the innersurfaces of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in .an inwardposition, and

(g) a raised abutment having channel cuts in the `top thereof extendsradially outwardly from the end of the duct so that the free end of theblow-in doors will contact it in an inward position.

12. In combination, an engine having:

(a) a duct for a first exhaust gas How,

(b) aps positioned to form a converging section adjacent the end of saidduct,

(c) a pod around said duct forming an annular space therewith,

(d) blow-in doors pivotally mounted at the end of said pod and extendingrearwardly, said doors being movable inwardly -to a point adjacent saidaps,

(e) an annular body positioned rearwardly of said pod with the innersurface of said body forming an inlet passageway with each door for asecond gas flow, and

(f) means for inducing turbulence where the doors end in an inwardposition, including,

(l) means for directing a third gas flow to mix with fluid flow passingtthrough said inlet passageways adjacent the ends of the blow-in doors,

(2) said directing means having opening means through which the lthirdgas flow passes.

(g) said means for directing a third flow of gas being movable so thatthe angle of iiow can be changed relative to the position of the end ofthe blow-in doors.

13. In combination, an engine as set forth in claim 11 wherein:

(h) the downstream end of the raised abutment has a solid flangeextending upwardly so that when the blow-in doors are resting on theabutment, the flange enters into each inlet passageway formed by theblow-in doors.

EVERETT W. KIRBY, Primary Examiner U.S. Cl. X.R.

